Global electrodynamics observed during the initial and main phases of the July 1991 magnetic storm
Global electrodynamics observed during the initial and main phases of the July 1991 magnetic storm
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DOI：
10.1029/2000ja000348
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发表时间：
2001-11
期刊：
影响因子：
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通讯作者：
G. Wilson;W. J. Burke;N. Maynard;Cheryl Y. Huang;H. Singer
中科院分区：
文献类型：
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作者：
G. Wilson;W. J. Burke;N. Maynard;Cheryl Y. Huang;H. Singer
由7颗偶然定位在行星际介质、磁层和顶侧电离层的卫星以及许多地面磁力计获得的数据使我们能够跟踪1991年7月8日至9日磁暴期间全球电流和电场的演变。7月8日，一个行星际扰动在1636 UT与磁层相撞，压缩了地球静止轨道内的磁层顶约3小时，这是由两颗GOES卫星上的磁力计观测到的。风暴分为四个部分发展，初始阶段和主要阶段之间有7小时的间歇期。初始阶段的特征是：（1）一个广泛的DP 2电流系统，产生了103500 nT的AE扰动，在昼侧有报告站;（2）极光电子通量增加了20倍;（3）内磁层立即出现电场。环电流的主相增强和向地运动与行星际磁场（IMF）的南转向和极帽电位在200 kV以上的增加有关。环电流增长的一个显着的部分之前，观察到的几个亚暴发生在主要和恢复阶段。恢复的开始的特点是减少向南的IMF分量，跨极冠电位和磁层电场。它还以亚风暴开始为标志。考虑到Dst调制相对于亚暴发生的时间，我们得出结论，在这次磁暴期间，负责环电流传输/环电流的电场主要与DP 2电流系统。最后，在夜晚扇区，初始和主阶段的穿透电场导致形成向上移动的赤道等离子体气泡，这是由两颗DMSP卫星在顶侧电离层中检测到的。
Data acquired by seven fortuitously positioned satellites in the interplanetary medium, the magnetosphere, and the topside ionosphere, as well as from numerous ground magnetometers have allowed us to follow the evolution of global currents and electric fields during the geomagnetic storm on July 8–9, 1991. An interplanetary disturbance collided with the magnetosphere at ∼1636 UT on July 8th, compressing the magnetopause inside of geostationary orbit for about 3 hours, as observed by magnetometers on two GOES satellites. The resulting storm developed in four segments with a 7 hour lull separating the initial and main phases. The initial phase was characterized by (1) an extensive, DP 2 current system that produced an AE perturbation of ∼3500 nT, with reporting stations on the dayside, (2) a twenty‐fold increase in auroral electron fluxes, and (3) the immediate appearance of electric fields in the inner magnetosphere. The main phase intensification and earthward movement of the ring current are associated with southward turnings of the interplanetary magnetic field (IMF) and a polar cap potential increase above 200 kV. A significant fraction of the ring current growth was observed prior to the first of several substorms that occurred during the main and recovery phases. The beginning of recovery was characterized by a diminution of the southward IMF component, the cross polar cap potential and magnetospheric electric fields. It was also marked by a substorm onset. Considering the timing of Dst modulations relative to substorm occurrence, we conclude that during this magnetic storm, the electric fields responsible for ring current transport/energization were mostly associated with the DP 2 current system. Finally, in the evening‐sector penetration electric fields of the initial and main phases led to the formation of upward moving equatorial plasma bubbles that were detected by two DMSP satellites in the topside ionosphere.